One acting too sweet for the circumstance; Unable to hold their alcohol in a social setting; Showing feminine characteristics in a predominently male environment.
Jason is such a sweetbul! He totally doesn't do any work and is drunk after only two beers. So sweet.
Supervillian that steals everything they can get a hold of and breaks the rest, usually for lulz. A sweetbunny is classically found on irc networks high out of its mind on psychedelic drugs.